Most homes use WiFi to connect their computers, tablets, gaming
consoles, printers, … to each other and to the Internet. WiFi is a lot
more convenient than cabled Ethernet but it is also a lot easier to
steal. WiFi routers, or access points, send out radio signals and some
of them leak past the walls of your home. That’s a good thing if you
want to use a laptop in the back yard but not such a good thing if
someone is freeloading your Internet connection from next door and
running up your bill. Nor is it good if they get access to your files.
The MAC address is burned into your hardware and every device in the world has a unique MAC address, it’s like a fingerprint. MAC addresses look something like this 12:34:56:78:9A:BC. When a PC wants to get on the network (usually when you turn it on) it sends its MAC address to the router and in return gets an IP address. Sometimes the IP address might be configured in the PC.
IP addresses can change from day to day. The router the IP addresses and matching MAC addresses to connect devices to the Internet. In order for any device to get on the Internet its address must be on the router’s address list. PCs keep similar lists if they need to connect to each other for file sharing, printing, or media streaming.
This list may be either an ARP list or a DHCP list. It doesn’t really matter which one; the point is that all devices using your network will be on this list. If someone is stealing your Internet, they’ll be on the list.
Sometimes you will see dashes and sometimes colons in MAC addresses. How to get the MAC and IP addresses will depend on the device type. Many devices will have the MAC address written on a label on the device close to the Ethernet port.
Make a list of all MAC address and IP addresses of all the devices on your home network. Note that devices will have different MAC addresses for Ethernet and WiFi.
Now go to the router and, this will depend on your router -so check the manual, find the DHCP table or the ARP table. On my Linksys they are both under Status, Local Network. The table will have both MAC and IP addresses and look something like this:
Now go through the list and check all the IP and MAC addresses you
found in your home inventory. For devices that you only have an IP for
you should take down the MAC address now.
Sometimes the DHCP table is easier to use than the ARP table because it usually shows device names as well which might make devices easier to identify.
You’ll have to check the list regularly if you want to catch someone in the act though because the entries in this list generally disappear after a few hours.
Unfortunately, once you find out that someone is stealing your internet it is next to impossible to find out who it is. But it isn’t hard to make sure that they don’t do it again. See Home WiFi Security.
Digital Fingerprints -MAC Addresses
Whenever a device gets on a network, it needs two things: a MAC address, and an IP address in order to send and receive data.The MAC address is burned into your hardware and every device in the world has a unique MAC address, it’s like a fingerprint. MAC addresses look something like this 12:34:56:78:9A:BC. When a PC wants to get on the network (usually when you turn it on) it sends its MAC address to the router and in return gets an IP address. Sometimes the IP address might be configured in the PC.
IP addresses can change from day to day. The router the IP addresses and matching MAC addresses to connect devices to the Internet. In order for any device to get on the Internet its address must be on the router’s address list. PCs keep similar lists if they need to connect to each other for file sharing, printing, or media streaming.
This list may be either an ARP list or a DHCP list. It doesn’t really matter which one; the point is that all devices using your network will be on this list. If someone is stealing your Internet, they’ll be on the list.
Make an Inventory of Your Network Devices
First you need to figure out who the good guys are and get their MAC addresses. You need to take an inventory of all your networked devices. If you can’t find the MAC address then settle for the IP address. For Windows PCs: open the Control Panel, Network and Internet, Network and Sharing Center, and you should see your network name. Click on the network name in the right column and a window will pop up. Click on Details and another window will pop up. Take down the physical address, which is the MAC address.Sometimes you will see dashes and sometimes colons in MAC addresses. How to get the MAC and IP addresses will depend on the device type. Many devices will have the MAC address written on a label on the device close to the Ethernet port.
Make a list of all MAC address and IP addresses of all the devices on your home network. Note that devices will have different MAC addresses for Ethernet and WiFi.
Now go to the router and, this will depend on your router -so check the manual, find the DHCP table or the ARP table. On my Linksys they are both under Status, Local Network. The table will have both MAC and IP addresses and look something like this:
Any Unknown Addresses?
If any address shows up on this list that doesn’t match with one of your devices then check again to make sure you have a complete inventory. If you are sure that it’s not one of yours then it is coming from somewhere else and someone is using your home network.Sometimes the DHCP table is easier to use than the ARP table because it usually shows device names as well which might make devices easier to identify.
You’ll have to check the list regularly if you want to catch someone in the act though because the entries in this list generally disappear after a few hours.
Unfortunately, once you find out that someone is stealing your internet it is next to impossible to find out who it is. But it isn’t hard to make sure that they don’t do it again. See Home WiFi Security.
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